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• setting up vpn server

  - by Lock

  I need help in visualising how to setup our VPN box when we move to our new network with Telstra. We have a safe@office 500P, which has a public IP and a private IP of 192.168.19.2. It is physically connected to our router, which has 4 different interfaces, one being 192.168.19.1. On the VPN box, we have a static route to forward everything to 192.168.19.1 which is the router, and from there it works out where to go. Now, we are moving to a Telstra WAN and things are setup a little differently. Our head office router has only 3 interfaces- 1 is for the link to the switch that has the fibre connection (so our route to the internet and other branches), 1 is for our 10.10.20.x network and one is for the local branch network. I really have no idea how to set this up as with the new setup, we will not have a port for it to plug into on the router. Could I just plug it into the 10.10.20.x network? Would I have to give it a public IP or can we just forward through the ports that it would use? Another suggestion was to VLAN our switch into two networks- one for the 10.10.20.x network and one for the network the VPN currently sits on (192.168.19.x), and setup the router to trunk between the port and the switch. Not sure how to do this. Sorry VPN's are definitely not my strong suit. Any advice appreciated!

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• Do I need to install mssql before I can use mssql.so with php on unix?

  - by lock

  I didn't install any MSSQL instance on my localhost that runs windows. I just used the xampp package and uncommented the modules used for mssql. The mssql server resides on another Windows Server so I believe I only needed a simple connector module. I hoped that it would be the same for Unix. But whenever I open my site on the unix production server, (i use codeigniter btw) the logs tell me it stops script execution after Database Driver Class Initialized. I am not really familiar on installing apache and friends on unix and I wasn't responsible on how the server was set-up. But it turns out that there is no mssql.so found on the php modules directory so i tried to google for one. While the forums are telling me to just compile the script, I couldn't just do that simply as I have no write access to the server and plus it seems upon installation of php, phpize didn't get installed with it too. Hope someone can shed light to me regarding this. I think its just easier if I can get a mssql.so for PHP 4.4.4

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• ActiveRecord and transactionsin between `before_save` and `save`

  - by JP

  I have some logic in before_save whereby (only) when some conditions are met I let the new row be created with special_number equal to the maximum special_number in the database + 1. (If the conditions aren't met then I do something different, so I can't use auto-increments) My worry is that two threads acting on this database at once might pick the same special_number if the second is executed while the first is saving. Is there way to lock the database between before_save and finishing the save, but only in some cases? I know all saves are sent in transactions, will this do the job for me? def before_save if things_are_just_right # -- Issue some kind of lock? # -- self.lock? I have no idea # Pick new special_number new_special = self.class.maximum('special_number') + 1 write_attribute('special_number',new_special) else # No need to lock in this case write_attribute('special_number',some_other_number) end end

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• Security in C# ?

  - by mehdi

  How can write a application in C# with security lock?(Adding a product key/unlock)

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• Pthread - setting scheduler parameters

  - by Andna

  I wanted to use read-writer locks from pthread library in a way, that writers have priority over readers. I read in my man pages that If the Thread Execution Scheduling option is supported, and the threads involved in the lock are executing with the scheduling policies SCHED_FIFO or SCHED_RR, the calling thread shall not acquire the lock if a writer holds the lock or if writers of higher or equal priority are blocked on the lock; otherwise, the calling thread shall acquire the lock. so I wrote small function that sets up thread scheduling options. void thread_set_up(int _thread) { struct sched_param *_param=malloc(sizeof (struct sched_param)); int *c=malloc(sizeof(int)); *c=sched_get_priority_min(SCHED_FIFO)+1; _param->__sched_priority=*c; long *a=malloc(sizeof(long)); *a=syscall(SYS_gettid); int *b=malloc(sizeof(int)); *b=SCHED_FIFO; if (pthread_setschedparam(*a,*b,_param) == -1) { //depending on which thread calls this functions, few thing can happen if (_thread == MAIN_THREAD) client_cleanup(); else if (_thread==ACCEPT_THREAD) { pthread_kill(params.main_thread_id,SIGINT); pthread_exit(NULL); } } } sorry for those a,b,c but I tried to malloc everything, still I get SIGSEGV on the call to pthread_setschedparam, I am wondering why?

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• unprotected access to member in property get

  - by Lenik

  I have a property public ObservableCollection<string> Name { get { return _nameCache; } } _nameCache is updated by multiple threads in other class methods. The updates are guarded by a lock. The question is: should I use the same lock around my return statement? Will not using a lock lead to a race condition?

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• Errors trying to run MongoDB

  - by SomeKittens

  I'm running Ubuntu Server 12.04 (32 bit) on an old (1998) computer. Everything's working fine until I try and start MongoDB. somekittens@DLserver01:~$ mongo MongoDB shell version: 2.2.2 connecting to: test Sun Dec 16 22:47:50 Error: couldn't connect to server 127.0.0.1:27017 src/mongo/shell/mongo.js:91 exception: connect failed Googling the error lead me to all sorts of "repair" options, none of which fixed anything. I've also removed MongoDB and installed it again (using apt-get, have not built from source). Mongo's log shows the following error: Thu Dec 13 18:36:32 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability. Thu Dec 13 18:36:32 Thu Dec 13 18:36:32 [initandlisten] MongoDB starting : pid=758 port=27017 dbpath=/var/lib/mongodb 32-bit host=DLserver01 Thu Dec 13 18:36:32 [initandlisten] Thu Dec 13 18:36:32 [initandlisten] ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data Thu Dec 13 18:36:32 [initandlisten] ** see http://blog.mongodb.org/post/137788967/32-bit-limitations Thu Dec 13 18:36:32 [initandlisten] ** with --journal, the limit is lower Thu Dec 13 18:36:32 [initandlisten] Thu Dec 13 18:36:32 [initandlisten] db version v2.2.2, pdfile version 4.5 Thu Dec 13 18:36:32 [initandlisten] git version: d1b43b61a5308c4ad0679d34b262c5af9d664267 Thu Dec 13 18:36:32 [initandlisten] build info: Linux domU-12-31-39-01-70-B4 2.6.21.7-2.fc8xen #1 SMP Fri Feb 15 12:39:36 EST 2008 i686 BOOST_LIB_VERSION=1_49 Thu Dec 13 18:36:32 [initandlisten] options: { config: "/etc/mongodb.conf", dbpath: "/var/lib/mongodb", logappend: "true", logpath: "/var/log/mongodb/mongodb.log" } Thu Dec 13 18:36:32 [initandlisten] Unable to check for journal files due to: boost::filesystem::basic_directory_iterator constructor: No such file or directory: "/var/lib/mongodb/journal" ************** Unclean shutdown detected. Please visit http://dochub.mongodb.org/core/repair for recovery instructions. ************* Thu Dec 13 18:36:32 [initandlisten] exception in initAndListen: 12596 old lock file, terminating Thu Dec 13 18:36:32 dbexit: Thu Dec 13 18:36:32 [initandlisten] shutdown: going to close listening sockets... Thu Dec 13 18:36:32 [initandlisten] shutdown: going to flush diaglog... Thu Dec 13 18:36:32 [initandlisten] shutdown: going to close sockets... Thu Dec 13 18:36:32 [initandlisten] shutdown: waiting for fs preallocator... Thu Dec 13 18:36:32 [initandlisten] shutdown: closing all files... Thu Dec 13 18:36:32 [initandlisten] closeAllFiles() finished Thu Dec 13 18:36:32 dbexit: really exiting now Running through the recovery instructions lead to the following adventure: somekittens@DLserver01:/var/log/mongodb$ mongod --repair Sun Dec 16 22:42:54 Sun Dec 16 22:42:54 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability. Sun Dec 16 22:42:54 Sun Dec 16 22:42:54 [initandlisten] MongoDB starting : pid=1887 port=27017 dbpath=/data/db/ 32-bit host=DLserver01 Sun Dec 16 22:42:54 [initandlisten] Sun Dec 16 22:42:54 [initandlisten] ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data Sun Dec 16 22:42:54 [initandlisten] ** see http://blog.mongodb.org/post/137788967/32-bit-limitations Sun Dec 16 22:42:54 [initandlisten] ** with --journal, the limit is lower Sun Dec 16 22:42:54 [initandlisten] Sun Dec 16 22:42:54 [initandlisten] db version v2.2.2, pdfile version 4.5 Sun Dec 16 22:42:54 [initandlisten] git version: d1b43b61a5308c4ad0679d34b262c5af9d664267 Sun Dec 16 22:42:54 [initandlisten] build info: Linux domU-12-31-39-01-70-B4 2.6.21.7-2.fc8xen #1 SMP Fri Feb 15 12:39:36 EST 2008 i686 BOOST_LIB_VERSION=1_49 Sun Dec 16 22:42:54 [initandlisten] options: { repair: true } Sun Dec 16 22:42:54 [initandlisten] exception in initAndListen: 10296 ********************************************************************* ERROR: dbpath (/data/db/) does not exist. Create this directory or give existing directory in --dbpath. See http://dochub.mongodb.org/core/startingandstoppingmongo ********************************************************************* , terminating Sun Dec 16 22:42:54 dbexit: Sun Dec 16 22:42:54 [initandlisten] shutdown: going to close listening sockets... Sun Dec 16 22:42:54 [initandlisten] shutdown: going to flush diaglog... Sun Dec 16 22:42:54 [initandlisten] shutdown: going to close sockets... Sun Dec 16 22:42:54 [initandlisten] shutdown: waiting for fs preallocator... Sun Dec 16 22:42:54 [initandlisten] shutdown: closing all files... Sun Dec 16 22:42:54 [initandlisten] closeAllFiles() finished Sun Dec 16 22:42:54 dbexit: really exiting now somekittens@DLserver01:/var/log/mongodb$ sudo mkdir /data somekittens@DLserver01:/var/log/mongodb$ sudo mkdir /data/db somekittens@DLserver01:/var/log/mongodb$ mongod --repair Sun Dec 16 22:43:51 Sun Dec 16 22:43:51 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability. Sun Dec 16 22:43:51 Sun Dec 16 22:43:51 [initandlisten] MongoDB starting : pid=1909 port=27017 dbpath=/data/db/ 32-bit host=DLserver01 Sun Dec 16 22:43:51 [initandlisten] Sun Dec 16 22:43:51 [initandlisten] ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data Sun Dec 16 22:43:51 [initandlisten] ** see http://blog.mongodb.org/post/137788967/32-bit-limitations Sun Dec 16 22:43:51 [initandlisten] ** with --journal, the limit is lower Sun Dec 16 22:43:51 [initandlisten] Sun Dec 16 22:43:51 [initandlisten] db version v2.2.2, pdfile version 4.5 Sun Dec 16 22:43:51 [initandlisten] git version: d1b43b61a5308c4ad0679d34b262c5af9d664267 Sun Dec 16 22:43:51 [initandlisten] build info: Linux domU-12-31-39-01-70-B4 2.6.21.7-2.fc8xen #1 SMP Fri Feb 15 12:39:36 EST 2008 i686 BOOST_LIB_VERSION=1_49 Sun Dec 16 22:43:51 [initandlisten] options: { repair: true } Sun Dec 16 22:43:51 [initandlisten] exception in initAndListen: 10309 Unable to create/open lock file: /data/db/mongod.lock errno:13 Permission denied Is a mongod instance already running?, terminating Sun Dec 16 22:43:51 dbexit: Sun Dec 16 22:43:51 [initandlisten] shutdown: going to close listening sockets... Sun Dec 16 22:43:51 [initandlisten] shutdown: going to flush diaglog... Sun Dec 16 22:43:51 [initandlisten] shutdown: going to close sockets... Sun Dec 16 22:43:51 [initandlisten] shutdown: waiting for fs preallocator... Sun Dec 16 22:43:51 [initandlisten] shutdown: closing all files... Sun Dec 16 22:43:51 [initandlisten] closeAllFiles() finished Sun Dec 16 22:43:51 [initandlisten] shutdown: removing fs lock... Sun Dec 16 22:43:51 [initandlisten] couldn't remove fs lock errno:9 Bad file descriptor Sun Dec 16 22:43:51 dbexit: really exiting now somekittens@DLserver01:/var/log/mongodb$ service mongodb stop stop: Unknown instance: somekittens@DLserver01:/var/log/mongodb$ sudo mongod --repair Sun Dec 16 22:45:04 Sun Dec 16 22:45:04 warning: 32-bit servers don't have journaling enabled by default. Please use --journal if you want durability. Sun Dec 16 22:45:04 Sun Dec 16 22:45:04 [initandlisten] MongoDB starting : pid=1921 port=27017 dbpath=/data/db/ 32-bit host=DLserver01 Sun Dec 16 22:45:04 [initandlisten] Sun Dec 16 22:45:04 [initandlisten] ** NOTE: when using MongoDB 32 bit, you are limited to about 2 gigabytes of data Sun Dec 16 22:45:04 [initandlisten] ** see http://blog.mongodb.org/post/137788967/32-bit-limitations Sun Dec 16 22:45:04 [initandlisten] ** with --journal, the limit is lower Sun Dec 16 22:45:04 [initandlisten] Sun Dec 16 22:45:04 [initandlisten] db version v2.2.2, pdfile version 4.5 Sun Dec 16 22:45:04 [initandlisten] git version: d1b43b61a5308c4ad0679d34b262c5af9d664267 Sun Dec 16 22:45:04 [initandlisten] build info: Linux domU-12-31-39-01-70-B4 2.6.21.7-2.fc8xen #1 SMP Fri Feb 15 12:39:36 EST 2008 i686 BOOST_LIB_VERSION=1_49 Sun Dec 16 22:45:04 [initandlisten] options: { repair: true } Sun Dec 16 22:45:04 [initandlisten] Unable to check for journal files due to: boost::filesystem::basic_directory_iterator constructor: No such file or directory: "/data/db/journal" Sun Dec 16 22:45:04 [initandlisten] finished checking dbs Sun Dec 16 22:45:04 dbexit: Sun Dec 16 22:45:04 [initandlisten] shutdown: going to close listening sockets... Sun Dec 16 22:45:04 [initandlisten] shutdown: going to flush diaglog... Sun Dec 16 22:45:04 [initandlisten] shutdown: going to close sockets... Sun Dec 16 22:45:04 [initandlisten] shutdown: waiting for fs preallocator... Sun Dec 16 22:45:04 [initandlisten] shutdown: closing all files... Sun Dec 16 22:45:04 [initandlisten] closeAllFiles() finished Sun Dec 16 22:45:04 [initandlisten] shutdown: removing fs lock... Sun Dec 16 22:45:04 dbexit: really exiting now Which didn't change anything. What can I do to resolve this? It's an old computer (640MB RAM, single-core P2). Could that be causing it?

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• Global Cache CR Requested But Current Block Received

  - by Liu Maclean(???)

  ????????«MINSCN?Cache Fusion Read Consistent» ????,???????????? ??????????????????: SQL> select * from V$version; BANNER -------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production PL/SQL Release 11.2.0.3.0 - Production CORE 11.2.0.3.0 Production TNS for Linux: Version 11.2.0.3.0 - Production NLSRTL Version 11.2.0.3.0 - Production SQL> select count(*) from gv$instance; COUNT(*) ---------- 2 SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- www.oracledatabase12g.com ?11gR2 2??RAC??????????status???XG,????Xcurrent block???INSTANCE 2?hold?,?????INSTANCE 1?????????,?????: SQL> select * from test; ID ---------- 1 2 SQL> select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from test; DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID) ------------------------------------ ------------------------------------ 89233 1 89233 1 SQL> alter system flush buffer_cache; System altered. INSTANCE 1 Session A: SQL> update test set id=id+1 where id=1; 1 row updated. INSTANCE 1 Session B: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1755287 SQL> oradebug setmypid; Statement processed. SQL> oradebug dump gc_elements 255; Statement processed. SQL> oradebug tracefile_name; /s01/orabase/diag/rdbms/vprod/VPROD1/trace/VPROD1_ora_19111.trc GLOBAL CACHE ELEMENT DUMP (address: 0xa4ff3080): id1: 0x15c91 id2: 0x1 pkey: OBJ#76896 block: (1/89233) lock: X rls: 0x0 acq: 0x0 latch: 3 flags: 0x20 fair: 0 recovery: 0 fpin: 'kdswh11: kdst_fetch' bscn: 0x0.146e20 bctx: (nil) write: 0 scan: 0x0 lcp: (nil) lnk: [NULL] lch: [0xa9f6a6f8,0xa9f6a6f8] seq: 32 hist: 58 145:0 118 66 144:0 192 352 197 48 121 113 424 180 58 LIST OF BUFFERS LINKED TO THIS GLOBAL CACHE ELEMENT: flg: 0x02000001 lflg: 0x1 state: XCURRENT tsn: 0 tsh: 2 addr: 0xa9f6a5c8 obj: 76896 cls: DATA bscn: 0x0.1ac898 BH (0xa9f6a5c8) file#: 1 rdba: 0x00415c91 (1/89233) class: 1 ba: 0xa9e56000 set: 5 pool: 3 bsz: 8192 bsi: 0 sflg: 3 pwc: 0,15 dbwrid: 0 obj: 76896 objn: 76896 tsn: 0 afn: 1 hint: f hash: [0x91f4e970,0xbae9d5b8] lru: [0x91f58848,0xa9f6a828] lru-flags: debug_dump obj-flags: object_ckpt_list ckptq: [0x9df6d1d8,0xa9f6a740] fileq: [0xa2ece670,0xbdf4ed68] objq: [0xb4964e00,0xb4964e00] objaq: [0xb4964de0,0xb4964de0] st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 2 le: 0xa4ff3080 flags: buffer_dirty redo_since_read LRBA: [0x19.5671.0] LSCN: [0x0.1ac898] HSCN: [0x0.1ac898] HSUB: [1] buffer tsn: 0 rdba: 0x00415c91 (1/89233) scn: 0x0000.001ac898 seq: 0x01 flg: 0x00 tail: 0xc8980601 frmt: 0x02 chkval: 0x0000 type: 0x06=trans data ??????block: (1/89233)?GLOBAL CACHE ELEMENT DUMP?LOCK????X ??XG , ??????Current Block????Instance??modify???,????????????? ????Instance 2 ????: Instance 2 Session C: SQL> update test set id=id+1 where id=2; 1 row updated. Instance 2 Session D: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1756658 SQL> oradebug setmypid; Statement processed. SQL> oradebug dump gc_elements 255; Statement processed. SQL> oradebug tracefile_name; /s01/orabase/diag/rdbms/vprod/VPROD2/trace/VPROD2_ora_13038.trc GLOBAL CACHE ELEMENT DUMP (address: 0x89fb25a0): id1: 0x15c91 id2: 0x1 pkey: OBJ#76896 block: (1/89233) lock: XG rls: 0x0 acq: 0x0 latch: 3 flags: 0x20 fair: 0 recovery: 0 fpin: 'kduwh01: kdusru' bscn: 0x0.1acdf3 bctx: (nil) write: 0 scan: 0x0 lcp: (nil) lnk: [NULL] lch: [0x96f4cf80,0x96f4cf80] seq: 61 hist: 324 21 143:0 19 16 352 329 144:6 14 7 352 197 LIST OF BUFFERS LINKED TO THIS GLOBAL CACHE ELEMENT: flg: 0x0a000001 state: XCURRENT tsn: 0 tsh: 1 addr: 0x96f4ce50 obj: 76896 cls: DATA bscn: 0x0.1acdf6 BH (0x96f4ce50) file#: 1 rdba: 0x00415c91 (1/89233) class: 1 ba: 0x96bd4000 set: 5 pool: 3 bsz: 8192 bsi: 0 sflg: 2 pwc: 0,15 dbwrid: 0 obj: 76896 objn: 76896 tsn: 0 afn: 1 hint: f hash: [0x96ee1fe8,0xbae9d5b8] lru: [0x96f4d0b0,0x96f4cdc0] obj-flags: object_ckpt_list ckptq: [0xbdf519b8,0x96f4d5a8] fileq: [0xbdf519d8,0xbdf519d8] objq: [0xb4a47b90,0xb4a47b90] objaq: [0x96f4d0e8,0xb4a47b70] st: XCURRENT md: NULL fpin: 'kduwh01: kdusru' tch: 1 le: 0x89fb25a0 flags: buffer_dirty redo_since_read remote_transfered LRBA: [0x11.9e18.0] LSCN: [0x0.1acdf6] HSCN: [0x0.1acdf6] HSUB: [1] buffer tsn: 0 rdba: 0x00415c91 (1/89233) scn: 0x0000.001acdf6 seq: 0x01 flg: 0x00 tail: 0xcdf60601 frmt: 0x02 chkval: 0x0000 type: 0x06=trans data GCS CLIENT 0x89fb2618,6 resp[(nil),0x15c91.1] pkey 76896.0 grant 2 cvt 0 mdrole 0x42 st 0x100 lst 0x20 GRANTQ rl G0 master 1 owner 2 sid 0 remote[(nil),0] hist 0x94121c601163423c history 0x3c.0x4.0xd.0xb.0x1.0xc.0x7.0x9.0x14.0x1. cflag 0x0 sender 1 flags 0x0 replay# 0 abast (nil).x0.1 dbmap (nil) disk: 0x0000.00000000 write request: 0x0000.00000000 pi scn: 0x0000.00000000 sq[(nil),(nil)] msgseq 0x1 updseq 0x0 reqids[6,0,0] infop (nil) lockseq x2b8 pkey 76896.0 hv 93 [stat 0x0, 1->1, wm 32768, RMno 0, reminc 18, dom 0] kjga st 0x4, step 0.0.0, cinc 20, rmno 6, flags 0x0 lb 0, hb 0, myb 15250, drmb 15250, apifrz 0 ?Instance 2??????block: (1/89233)? GLOBAL CACHE ELEMENT Lock Convert?lock: XG ????GC_ELEMENTS DUMP???XCUR Cache Fusion?,???????X$ VIEW,??? X$LE X$KJBR X$KJBL, ???X$ VIEW???????????????????: INSTANCE 2 Session D: SELECT * FROM x$le WHERE le_addr IN (SELECT le_addr FROM x$bh WHERE obj IN (SELECT data_object_id FROM dba_objects WHERE owner = 'SYS' AND object_name = 'TEST') AND class = 1 AND state != 3); ADDR INDX INST_ID LE_ADDR LE_ID1 LE_ID2 ---------------- ---------- ---------- ---------------- ---------- ---------- LE_RLS LE_ACQ LE_FLAGS LE_MODE LE_WRITE LE_LOCAL LE_RECOVERY ---------- ---------- ---------- ---------- ---------- ---------- ----------- LE_BLKS LE_TIME LE_KJBL ---------- ---------- ---------------- 00007F94CA14CF60 7003 2 0000000089FB25A0 89233 1 0 0 32 2 0 1 0 1 0 0000000089FB2618 PCM Resource NAME?[ID1][ID2],[BL]???, ID1?ID2 ??blockno? fileno????, ??????????GC_elements dump?? id1: 0x15c91 id2: 0×1 pkey: OBJ#76896 block: (1/89233)?? ,?  kjblname ? kjbrname ??”[0x15c91][0x1],[BL]” ??: INSTANCE 2 Session D: SQL> set linesize 80 pagesize 1400 SQL> SELECT * 2 FROM x$kjbl l 3 WHERE l.kjblname LIKE '%[0x15c91][0x1],[BL]%'; ADDR INDX INST_ID KJBLLOCKP KJBLGRANT KJBLREQUE ---------------- ---------- ---------- ---------------- --------- --------- KJBLROLE KJBLRESP KJBLNAME ---------- ---------------- ------------------------------ KJBLNAME2 KJBLQUEUE ------------------------------ ---------- KJBLLOCKST KJBLWRITING ---------------------------------------------------------------- ----------- KJBLREQWRITE KJBLOWNER KJBLMASTER KJBLBLOCKED KJBLBLOCKER KJBLSID KJBLRDOMID ------------ ---------- ---------- ----------- ----------- ---------- ---------- KJBLPKEY ---------- 00007F94CA22A288 451 2 0000000089FB2618 KJUSEREX KJUSERNL 0 00 [0x15c91][0x1],[BL][ext 0x0,0x 89233,1,BL 0 GRANTED 0 0 1 0 0 0 0 0 76896 SQL> SELECT r.* FROM x$kjbr r WHERE r.kjbrname LIKE '%[0x15c91][0x1],[BL]%'; no rows selected Instance 1 session B: SQL> SELECT r.* FROM x$kjbr r WHERE r.kjbrname LIKE '%[0x15c91][0x1],[BL]%'; ADDR INDX INST_ID KJBRRESP KJBRGRANT KJBRNCVL ---------------- ---------- ---------- ---------------- --------- --------- KJBRROLE KJBRNAME KJBRMASTER KJBRGRANTQ ---------- ------------------------------ ---------- ---------------- KJBRCVTQ KJBRWRITER KJBRSID KJBRRDOMID KJBRPKEY ---------------- ---------------- ---------- ---------- ---------- 00007F801ACA68F8 1355 1 00000000B5A62AE0 KJUSEREX KJUSERNL 0 [0x15c91][0x1],[BL][ext 0x0,0x 0 00000000B48BB330 00 00 0 0 76896 ??????Instance 1???block: (1/89233),??????Instance 2 build cr block ????Instance 1, ?????????? ????? Instance 1? Foreground Process ? Instance 2?LMS??????RAC  TRACE: Instance 2: [oracle@vrh2 ~]$ ps -ef|grep ora_lms|grep -v grep oracle 23364 1 0 Apr29 ? 00:33:15 ora_lms0_VPROD2 SQL> oradebug setospid 23364 Oracle pid: 13, Unix process pid: 23364, image: [email protected] (LMS0) SQL> oradebug event 10046 trace name context forever,level 8:10708 trace name context forever,level 103: trace[rac.*] disk high; Statement processed. SQL> oradebug tracefile_name /s01/orabase/diag/rdbms/vprod/VPROD2/trace/VPROD2_lms0_23364.trc Instance 1 session B : SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1756658 3 1756661 3 1755287 Instance 1 session A : SQL> alter session set events '10046 trace name context forever,level 8:10708 trace name context forever,level 103: trace[rac.*] disk high'; Session altered. SQL> select * from test; ID ---------- 2 2 SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1761520 ?x$BH?????,???????Instance 1???build??CR block,????? TRACE ??: Instance 1 foreground Process: PARSING IN CURSOR #140336527348792 len=18 dep=0 uid=0 oct=3 lid=0 tim=1335939136125254 hv=1689401402 ad='b1a4c828' sqlid='c99yw1xkb4f1u' select * from test END OF STMT PARSE #140336527348792:c=2999,e=2860,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=1357081020,tim=1335939136125253 EXEC #140336527348792:c=0,e=40,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=1357081020,tim=1335939136125373 WAIT #140336527348792: nam='SQL*Net message to client' ela= 6 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1335939136125420 *** 2012-05-02 02:12:16.125 kclscrs: req=0 block=1/89233 2012-05-02 02:12:16.125574 : kjbcro[0x15c91.1 76896.0][4] *** 2012-05-02 02:12:16.125 kclscrs: req=0 typ=nowait-abort *** 2012-05-02 02:12:16.125 kclscrs: bid=1:3:1:0:f:1e:0:0:10:0:0:0:1:2:4:1:20:0:0:0:c3:49:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:4:3:2:1:2:0:1c:0:4d:26:a3:52:0:0:0:0:c7:c:ca:62:c3:49:0:0:0:0:1:0:14:8e:47:76:1:2:dc:5:a9:fe:17:75:0:0:0:0:0:0:0:0:0:0:0:0:99:ed:0:0:0:0:0:0:10:0:0:0 2012-05-02 02:12:16.125718 : kjbcro[0x15c91.1 76896.0][4] 2012-05-02 02:12:16.125751 : GSIPC:GMBQ: buff 0xba0ee018, queue 0xbb79a7b8, pool 0x60013fa0, freeq 0, nxt 0xbb79a7b8, prv 0xbb79a7b8 2012-05-02 02:12:16.125780 : kjbsentscn[0x0.1ae0f0][to 2] 2012-05-02 02:12:16.125806 : GSIPC:SENDM: send msg 0xba0ee088 dest x20001 seq 177740 type 36 tkts xff0000 mlen x1680198 2012-05-02 02:12:16.125918 : kjbmscr(0x15c91.1)reqid=0x8(req 0xa4ff30f8)(rinst 1)hldr 2(infosz 200)(lseq x2b8) 2012-05-02 02:12:16.126959 : GSIPC:KSXPCB: msg 0xba0ee088 status 30, type 36, dest 2, rcvr 1 *** 2012-05-02 02:12:16.127 kclwcrs: wait=0 tm=1233 *** 2012-05-02 02:12:16.127 kclwcrs: got 1 blocks from ksxprcv WAIT #140336527348792: nam='gc cr block 2-way' ela= 1233 p1=1 p2=89233 p3=1 obj#=76896 tim=1335939136127199 2012-05-02 02:12:16.127272 : kjbcrcomplete[0x15c91.1 76896.0][0] 2012-05-02 02:12:16.127309 : kjbrcvdscn[0x0.1ae0f0][from 2][idx 2012-05-02 02:12:16.127329 : kjbrcvdscn[no bscn <= rscn 0x0.1ae0f0][from 2] ???? kjbcro[0x15c91.1 76896.0][4] kjbsentscn[0x0.1ae0f0][to 2] ?Instance 2??SCN=1ae0f0=1761520? block: (1/89233),???’gc cr block 2-way’ ??,?????????CR block? Instance 2 LMS TRACE 2012-05-02 02:12:15.634057 : GSIPC:RCVD: ksxp msg 0x7f16e1598588 sndr 1 seq 0.177740 type 36 tkts 0 2012-05-02 02:12:15.634094 : GSIPC:RCVD: watq msg 0x7f16e1598588 sndr 1, seq 177740, type 36, tkts 0 2012-05-02 02:12:15.634108 : GSIPC:TKT: collect msg 0x7f16e1598588 from 1 for rcvr -1, tickets 0 2012-05-02 02:12:15.634162 : kjbrcvdscn[0x0.1ae0f0][from 1][idx 2012-05-02 02:12:15.634186 : kjbrcvdscn[no bscn1, wm 32768, RMno 0, reminc 18, dom 0] kjga st 0x4, step 0.0.0, cinc 20, rmno 6, flags 0x0 lb 0, hb 0, myb 15250, drmb 15250, apifrz 0 GCS CLIENT END 2012-05-02 02:12:15.635211 : kjbdowncvt[0x15c91.1 76896.0][1][options x0] 2012-05-02 02:12:15.635230 : GSIPC:AMBUF: rcv buff 0x7f16e1c56420, pool rcvbuf, rqlen 1103 2012-05-02 02:12:15.635308 : GSIPC:GPBMSG: new bmsg 0x7f16e1c56490 mb 0x7f16e1c56420 msg 0x7f16e1c564b0 mlen 152 dest x101 flushsz -1 2012-05-02 02:12:15.635334 : kjbmslset(0x15c91.1)) seq 0x4 reqid=0x6 (shadow 0xb48bb330.xb)(rsn 2)(mas@1) 2012-05-02 02:12:15.635355 : GSIPC:SPBMSG: send bmsg 0x7f16e1c56490 blen 184 msg 0x7f16e1c564b0 mtype 33 attr|dest x30101 bsz|fsz x1ffff 2012-05-02 02:12:15.635377 : GSIPC:SNDQ: enq msg 0x7f16e1c56490, type 65521 seq 118669, inst 1, receiver 1, queued 1 *** 2012-05-02 02:12:15.635 kclccctx: cleanup copy 0x7f16e1d94798 2012-05-02 02:12:15.635479 : [kjmpmsgi:compl][type 36][msg 0x7f16e1598588][seq 177740.0][qtime 0][ptime 1257] 2012-05-02 02:12:15.635511 : GSIPC:BSEND: flushing sndq 0xb491dd28, id 1, dcx 0xbc516778, inst 1, rcvr 1 qlen 0 1 2012-05-02 02:12:15.635536 : GSIPC:BSEND: no batch1 msg 0x7f16e1c56490 type 65521 len 184 dest (1:1) 2012-05-02 02:12:15.635557 : kjbsentscn[0x0.1ae0f1][to 1] 2012-05-02 02:12:15.635578 : GSIPC:SENDM: send msg 0x7f16e1c56490 dest x10001 seq 118669 type 65521 tkts x10002 mlen xb800e8 WAIT #0: nam='gcs remote message' ela= 180 waittime=1 poll=0 event=0 obj#=0 tim=1335939135635819 2012-05-02 02:12:15.635853 : GSIPC:RCVD: ksxp msg 0x7f16e167e0b0 sndr 1 seq 0.177741 type 32 tkts 0 2012-05-02 02:12:15.635875 : GSIPC:RCVD: watq msg 0x7f16e167e0b0 sndr 1, seq 177741, type 32, tkts 0 2012-05-02 02:12:15.636012 : GSIPC:TKT: collect msg 0x7f16e167e0b0 from 1 for rcvr -1, tickets 0 2012-05-02 02:12:15.636040 : kjbrcvdscn[0x0.1ae0f1][from 1][idx 2012-05-02 02:12:15.636060 : kjbrcvdscn[no bscn <= rscn 0x0.1ae0f1][from 1] 2012-05-02 02:12:15.636082 : GSIPC:TKT: dest (1:1) rtkt not acked 1  unassigned bufs 0  tkts 0  newbufs 0 2012-05-02 02:12:15.636102 : GSIPC:TKT: remove ctx dest (1:1) 2012-05-02 02:12:15.636125 : [kjmxmpm][type 32][seq 0.177741][msg 0x7f16e167e0b0][from 1] 2012-05-02 02:12:15.636146 : kjbmpocr(0xb0.6)seq 0x1,reqid=0x23a,(client 0x9fff7b58,0x1)(from 1)(lseq xdf0) 2????LMS????????? ??gcs remote message GSIPC ????SCN=[0x0.1ae0f0] block=1/89233???,??BAST kjbmpbast(0x15c91.1),?? block=1/89233??????? ??fairness??(?11.2.0.3???_fairness_threshold=2),?current block?KCL: F156: fairness downconvert,?Xcurrent DownConvert? Scurrent: Instance 2: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 2 0 3 1756658 ??Instance 2 LMS ?cr block??? kjbmslset(0x15c91.1)) ????SEND QUEUE GSIPC:SNDQ: enq msg 0x7f16e1c56490? ???????Instance 1???? block: (1/89233)??? ??????: Instance 2: SQL> select CURRENT_RESULTS,LIGHT_WORKS from v$cr_block_server; CURRENT_RESULTS LIGHT_WORKS --------------- ----------- 29273 437 Instance 1 session A: SQL> SQL> select * from test; ID ---------- 2 2 SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 3 1761942 3 1761932 1 0 3 1761520 Instance 2: SQL> select CURRENT_RESULTS,LIGHT_WORKS from v$cr_block_server; CURRENT_RESULTS LIGHT_WORKS --------------- ----------- 29274 437 select * from test END OF STMT PARSE #140336529675592:c=0,e=337,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=1357081020,tim=1335939668940051 EXEC #140336529675592:c=0,e=96,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=1357081020,tim=1335939668940204 WAIT #140336529675592: nam='SQL*Net message to client' ela= 5 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1335939668940348 *** 2012-05-02 02:21:08.940 kclscrs: req=0 block=1/89233 2012-05-02 02:21:08.940676 : kjbcro[0x15c91.1 76896.0][5] *** 2012-05-02 02:21:08.940 kclscrs: req=0 typ=nowait-abort *** 2012-05-02 02:21:08.940 kclscrs: bid=1:3:1:0:f:21:0:0:10:0:0:0:1:2:4:1:20:0:0:0:c3:49:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:0:4:3:2:1:2:0:1f:0:4d:26:a3:52:0:0:0:0:c7:c:ca:62:c3:49:0:0:0:0:1:0:17:8e:47:76:1:2:dc:5:a9:fe:17:75:0:0:0:0:0:0:0:0:0:0:0:0:99:ed:0:0:0:0:0:0:10:0:0:0 2012-05-02 02:21:08.940799 : kjbcro[0x15c91.1 76896.0][5] 2012-05-02 02:21:08.940833 : GSIPC:GMBQ: buff 0xba0ee018, queue 0xbb79a7b8, pool 0x60013fa0, freeq 0, nxt 0xbb79a7b8, prv 0xbb79a7b8 2012-05-02 02:21:08.940859 : kjbsentscn[0x0.1ae28c][to 2] 2012-05-02 02:21:08.940870 : GSIPC:SENDM: send msg 0xba0ee088 dest x20001 seq 177810 type 36 tkts xff0000 mlen x1680198 2012-05-02 02:21:08.940976 : kjbmscr(0x15c91.1)reqid=0xa(req 0xa4ff30f8)(rinst 1)hldr 2(infosz 200)(lseq x2b8) 2012-05-02 02:21:08.941314 : GSIPC:KSXPCB: msg 0xba0ee088 status 30, type 36, dest 2, rcvr 1 *** 2012-05-02 02:21:08.941 kclwcrs: wait=0 tm=707 *** 2012-05-02 02:21:08.941 kclwcrs: got 1 blocks from ksxprcv 2012-05-02 02:21:08.941818 : kjbassume[0x15c91.1][sender 2][mymode x1][myrole x0][srole x0][flgs x0][spiscn 0x0.0][swscn 0x0.0] 2012-05-02 02:21:08.941852 : kjbrcvdscn[0x0.1ae28d][from 2][idx 2012-05-02 02:21:08.941871 : kjbrcvdscn[no bscn ??????????????SCN=[0x0.1ae28c]=1761932 Version?CR block, ????receive????Xcurrent Block??SCN=1ae28d=1761933,Instance 1???Xcurrent Block???build????????SCN=1761932?CR BLOCK, ????????Current block,?????????'gc current block 2-way'? ?????????????request current block,?????kjbcro;?????Instance 2?LMS???????Current Block: Instance 2 LMS trace: 2012-05-02 02:21:08.448743 : GSIPC:RCVD: ksxp msg 0x7f16e14a4398 sndr 1 seq 0.177810 type 36 tkts 0 2012-05-02 02:21:08.448778 : GSIPC:RCVD: watq msg 0x7f16e14a4398 sndr 1, seq 177810, type 36, tkts 0 2012-05-02 02:21:08.448798 : GSIPC:TKT: collect msg 0x7f16e14a4398 from 1 for rcvr -1, tickets 0 2012-05-02 02:21:08.448816 : kjbrcvdscn[0x0.1ae28c][from 1][idx 2012-05-02 02:21:08.448834 : kjbrcvdscn[no bscn <= rscn 0x0.1ae28c][from 1] 2012-05-02 02:21:08.448857 : GSIPC:TKT: dest (1:1) rtkt not acked 2  unassigned bufs 0  tkts 0  newbufs 0 2012-05-02 02:21:08.448875 : GSIPC:TKT: remove ctx dest (1:1) 2012-05-02 02:21:08.448970 : [kjmxmpm][type 36][seq 0.177810][msg 0x7f16e14a4398][from 1] 2012-05-02 02:21:08.448993 : kjbmpbast(0x15c91.1) reqid=0x6 (req 0xa4ff30f8)(reqinst 1)(reqid 10)(flags x0) *** 2012-05-02 02:21:08.449 kclcrrf: req=48054 block=1/89233 *** 2012-05-02 02:21:08.449 kcl_compress_block: compressed: 6 free space: 7680 2012-05-02 02:21:08.449085 : kjbsentscn[0x0.1ae28d][to 1] 2012-05-02 02:21:08.449142 : kjbdeliver[to 1][0xa4ff30f8][10][current 1] 2012-05-02 02:21:08.449164 : kjbmssch(reqlock 0xa4ff30f8,10)(to 1)(bsz 344) 2012-05-02 02:21:08.449183 : GSIPC:AMBUF: rcv buff 0x7f16e18bcec8, pool rcvbuf, rqlen 1102 *** 2012-05-02 02:21:08.449 kclccctx: cleanup copy 0x7f16e1d94838 *** 2012-05-02 02:21:08.449 kcltouched: touch seconds 3271 *** 2012-05-02 02:21:08.449 kclgrantlk: req=48054 2012-05-02 02:21:08.449347 : [kjmpmsgi:compl][type 36][msg 0x7f16e14a4398][seq 177810.0][qtime 0][ptime 1119] WAIT #0: nam='gcs remote message' ela= 568 waittime=1 poll=0 event=0 obj#=0 tim=1335939668449962 2012-05-02 02:21:08.450001 : GSIPC:RCVD: ksxp msg 0x7f16e1bb22a0 sndr 1 seq 0.177811 type 32 tkts 0 2012-05-02 02:21:08.450024 : GSIPC:RCVD: watq msg 0x7f16e1bb22a0 sndr 1, seq 177811, type 32, tkts 0 2012-05-02 02:21:08.450043 : GSIPC:TKT: collect msg 0x7f16e1bb22a0 from 1 for rcvr -1, tickets 0 2012-05-02 02:21:08.450060 : kjbrcvdscn[0x0.1ae28e][from 1][idx 2012-05-02 02:21:08.450078 : kjbrcvdscn[no bscn <= rscn 0x0.1ae28e][from 1] 2012-05-02 02:21:08.450097 : GSIPC:TKT: dest (1:1) rtkt not acked 3  unassigned bufs 0  tkts 0  newbufs 0 2012-05-02 02:21:08.450116 : GSIPC:TKT: remove ctx dest (1:1) 2012-05-02 02:21:08.450136 : [kjmxmpm][type 32][seq 0.177811][msg 0x7f16e1bb22a0][from 1] 2012-05-02 02:21:08.450155 : kjbmpocr(0xb0.6)seq 0x1,reqid=0x23e,(client 0x9fff7b58,0x1)(from 1)(lseq xdf4) ???Instance 2??LMS???,???build cr block,??????Instance 1?????Current Block??????Instance 2??v$cr_block_server??????LIGHT_WORKS?????current block transfer??????,??????? CR server? Light Work Rule(Light Work Rule?8i Cr Server?????????,?Remote LMS?? build CR????????,resource holder?LMS???????block,????CR build If creating the consistent read version block involves too much work (such as reading blocks from disk), then the holder sends the block to the requestor, and the requestor completes the CR fabrication. The holder maintains a fairness counter of CR requests. After the fairness threshold is reached, the holder downgrades it to lock mode.)? ??????? CR Request ????Current Block?? ???:??????class?block,CR server??????? ??undo block?? undo header block?CR quest, LMS????Current Block, ????? ???? ??????? block cleanout? CR  Version??????? ???????? data blocks, ??????? CR quest  & CR received?(???????Light Work Rule,LMS"??"), ??Current Block??DownConvert???S lock,??LMS???????ship??current version?block? ??????? , ?????? ,???????DownConvert?????”_fairness_threshold“???200,????Xcurrent Block?????Scurrent, ????LMS?????Current Version?Data Block: SQL> show parameter fair NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ _fairness_threshold integer 200 Instance 1: SQL> update test set id=id+1 where id=4; 1 row updated. Instance 2: SQL> update test set id=id+1 where id=2; 1 row updated. SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1838166 ?Instance 1? ????,? ??instance 2? v$cr_block_server?? instance 1 SQL> select * from test; ID ---------- 10 3 instance 2: SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1883707 8 0 SQL> select * from test; ID ---------- 10 3 SQL> select state,cr_scn_bas from x$bh where file#=1 and dbablk=89233 and state!=0; STATE CR_SCN_BAS ---------- ---------- 1 0 3 1883707 8 0 ................... SQL> / STATE CR_SCN_BAS ---------- ---------- 2 0 3 1883707 3 1883695 repeat cr request on Instance 1 SQL> / STATE CR_SCN_BAS ---------- ---------- 8 0 3 1883707 3 1883695 ??????_fairness_threshold????????,?????200 ????????CR serve??Downgrade?lock, ????data block? CR Request????Receive? Current Block?

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• July, the 31 Days of SQL Server DMO’s – Day 24 (sys.dm_db_index_operational_stats)

  - by Tamarick Hill

  The sys.dm_db_index_operational_stats Dynamic Management Function returns information about the IO, locking, and access methods for the indexes that you currently have on your SQL Server Instance. This function takes four input parameters which are (1) database_id, (2) object_id, (3) index_id, and (4) partition_number. Let’s have a look at the results from this function against our AdventureWorks2012 database. This function returns a ton of columns, so not only will I not attempt to describe each of the columns, I wont even attempt to display all of them here. My query below will give you a subset of the columns returned from this function. SELECT database_id, object_id, index_id, partition_number, leaf_insert_count, leaf_delete_count, leaf_update_count, leaf_ghost_count, nonleaf_insert_count, nonleaf_delete_count, nonleaf_update_count, range_scan_count, forwarded_fetch_count, row_lock_count, row_lock_wait_count, page_lock_count, page_lock_wait_count, Index_lock_promotion_attempt_count, index_lock_promotion_count, page_compression_attempt_count, page_compression_success_count FROM sys.dm_db_index_operational_stats(db_id('AdventureWorks2012'), NULL, NULL, NULL) The first four columns in the result set represent the values that we passed in as our input parameters. If you use NULL’s as I did, then you will see results for every index on your system. I specified a database_id so my result set only shows those records pertaining to my AdventureWorks2012 database. The next columns in the result set provide you with information on how may inserts, deletes, or updates that have taken place on your leaf and nonleaf index levels. The nonleaf levels would refer to the intermediate and root index levels. In the middle of these you see a leaf_ghost_count column, which represents the number of records that have been logically deleted and marked as “ghosted”  and are waiting on the background ghost cleanup process to physically remove them. The range_scan_count column represents the number of range or table scans that have been performed against an index. The forwarded_fetch_count column represents the number of rows that were returned from a forwarding row pointer. The row_lock_count and row_lock_wait_count represent the number of row locks that have been requested for an index and the number of times SQL has had to wait on a row lock respectively. The page_lock_count and page_lock_wait_count represent the number of page locks that have been requested for an index and the number of times SQL has had to wait on a page lock respectively. The index_lock_promotion_attempt_count represents the number of times the database engine has attempted to promote a lock to the index level. The index_lock_promotion_count column displays how many times that index lock promotion was successful. Lastly the page_compression_attempt_count and page_compression_success_count represents how many times a page was attempted to be compressed and how many times the attempt was successful. As you can see there is a ton of information returned from this DMV. The DMV we reviewed on yesterday (sys.dm_db_index_usage_stats) provided you with good information on when and how indexes have been used, but this DMF takes an even deeper dive into these statistics. If you are interested in performing a very detailed analysis on the operational stats of your indexes, this is not only a good place to start, but more than likely the best place. For more information on this Dynamic Management Function, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms174281.aspx Follow me on Twitter @PrimeTimeDBA

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• JRockit Virtual Edition Debug Key

  - by changjae.lee

  There are a few keys that can help the debugging of the JRVE env in console. you can type in each keys in JRVE console to see what's happening under the hood. key '0' : System information key '5' : Enable shutdown key '7' : Start JRockit Management Server (port 7091) key '8' : Statistics Counters key '9' : Full Thread Dump key '0' : Status of Debug-key Below is the sample out from each keys. Debug-key '1' pressed ============ JRockitVE System Information ============ JRockitVE version : 11.1.1.3.0-67-131044 Kernel version : 6.1.0.0-97-131024 JVM version : R27.6.6-28_o-125824-1.6.0_17-20091214-2104-linux-ia32 Hypervisor version : Xen 3.4.0 Boot state : 0x007effff Uptime : 0 days 02:04:31 CPU : uniprocessor @2327 Mhz CPU usage : 0% ctx/s: 285 preempt/s: 0 migrations/s: 0 Physical pages : 82379/261121 (321/1020 MB) Network info : 10.179.97.64 (10.179.97.64/255.255.254.0) GateWay : 10.179.96.1 MAC address : 00:16:3e:7e:dc:78 Boot options : vfsCwd : /application/user_projects/domains/wlsve_domain mainArgs : java -javaagent:/jrockitve/services/sshd/sshd.jar -cp /jrockitve/jrockit/lib/tools.jar:/jrockitve/lib/common.jar:/application/patch_wls1032/profiles/default/sys_manifest_classpath/weblogic_patch.jar:/application/wlserver_10.3/server/lib/weblogic.jar -Dweblogic.Name=WlsveAdmin -Dweblogic.Domain=wlsve_domain -Dweblogic.management.username=weblogic -Dweblogic.management.password=welcome1 -Dweblogic.management.GenerateDefaultConfig=true weblogic.Server consLog : /jrockitve/log/jrockitve.log mounts : ext2 / dev0; posixLocale : en_US posixTimezone : Asia/Seoul posixEncoding : ISO-8859-1 Local disk : Size: 1024M, Used: 728M, Free: 295M ======================================================== Debug-key '5' pressed Shutdown enabled. Debug-key '7' pressed [JRockit] Management server already started. Ignoring request. Debug-key '8' pressed Starting stat recording Debug-key '8' pressed ========= Statistics Counters for the last second ========= dev.eth0_rx.cnt : 22 packets dev.eth0_rx_bytes.cnt : 2704 bytes dev.net_interrupts.cnt : 22 interrupts evt.timer_ticks.cnt : 123 ticks hyper.priv_entries.cnt : 144 entries schedule.context_switches.cnt : 271 switches schedule.idle_cpu_time.cnt : 997318849 nanoseconds schedule.idle_cpu_time_0.cnt : 997318849 nanoseconds schedule.total_cpu_time.cnt : 1000031757 nanoseconds time.system_time.cnt : 1000 ns time.timer_updates.cnt : 123 updates time.wallclock_time.cnt : 1000 ns ======================================= Debug-key '9' pressed ===== FULL THREAD DUMP =============== Fri Jun 4 08:22:12 2010 BEA JRockit(R) R27.6.6-28_o-125824-1.6.0_17-20091214-2104-linux-ia32 "Main Thread" id=1 idx=0x4 tid=1 prio=5 alive, in native, waiting -- Waiting for notification on: weblogic/t3/srvr/T3Srvr@0x646ede8[fat lock] at jrockit/vm/Threads.waitForNotifySignal(JLjava/lang/Object;)Z(Native Method) at java/lang/Object.wait(J)V(Native Method) at java/lang/Object.wait(Object.java:485) at weblogic/t3/srvr/T3Srvr.waitForDeath(T3Srvr.java:919) ^-- Lock released while waiting: weblogic/t3/srvr/T3Srvr@0x646ede8[fat lock] at weblogic/t3/srvr/T3Srvr.run(T3Srvr.java:479) at weblogic/Server.main(Server.java:67) at jrockit/vm/RNI.c2java(IIIII)V(Native Method) -- end of trace "(Signal Handler)" id=2 idx=0x8 tid=2 prio=5 alive, in native, daemon Open lock chains ================ Chain 1: "ExecuteThread: '0' for queue: 'weblogic.socket.Muxer'" id=23 idx=0x50 tid=20 waiting for java/lang/String@0x630c588 held by: "ExecuteThread: '1' for queue: 'weblogic.socket.Muxer'" id=24 idx=0x54 tid=21 (active) ===== END OF THREAD DUMP =============== Debug-key '0' pressed Debug-keys enabled Happy Cloud Walking :)

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• Ubuntu 12.10 Screensaver/blanking problem

  - by Ramon J. Strauff

  I have upgraded to 12.10 and then downgraded again to 12.04 LTS because of the screensaver or screen blanking problem. After 10-12 minutes the screen goes black/blank when i dont do anything (idle). I have tried setting in the Brightness and Lock menu that the screen should never lock or turn off if idle. This is very annoying when watching movies etc... Would be nice if someone knows this.... Thanks...

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• My screen turns off when I watch movies on YouTube [duplicate]

  - by Radu Radeanu

  This question already has an answer here: How to prevent my screen from dimming when watching YouTube? 4 answers When I use VLC or other media player, I can watch the movie until the end without touching the PC. If I watch a movie on YouTube using Chromium or Firefox my screen will turn off as is set in System Settings Brightness and Lock. How to prevent this without to change the settings in Brightness and Lock. Edit: My Ubuntu 13.04 with Gnome 3.6.3.1 uses gnome-screensaver (I didn't installed any other screensaver).

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• Avoiding Heap Contention Among Threads

  Allocating memory from the system heap can be an expensive operation due to a lock used by system runtime libraries to synchronize access to the heap. Contention on this lock can limit the performance benefits from multithreading. Learn how to solve this problem.

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• Avoiding Heap Contention Among Threads

  Allocating memory from the system heap can be an expensive operation due to a lock used by system runtime libraries to synchronize access to the heap. Contention on this lock can limit the performance benefits from multithreading. Learn how to solve this problem.

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• How can I choose which menubar indicators are shown in 12.04?

  - by Nicholas Weininger

  I'd like to be able to tweak the set of shortcuts on the right side of the menubar in 12.04 (e.g. remove the email shortcut, remove the wifi shortcut on my laptop, add a lock screen shortcut so I can lock the screen with a single click rather than facing the choice between two clicks and Ctrl-Alt-L). Is this possible? The only thing I can find to configure in the settings is the date/time display.

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• Varnish gets in a restart loop and causes the system to lock up; how can I fix?

  - by chrism2671

  Here is an extract from the syslog. Mar 2 14:01:10 ip-10-226-34-17 varnishd[20204]: Child (20205) not responding to ping, killing it. Mar 2 14:01:16 ip-10-226-34-17 varnishd[20204]: Child (20205) not responding to ping, killing it. Mar 2 14:01:16 ip-10-226-34-17 varnishd[20204]: Child (20205) died signal=3 Mar 2 14:01:21 ip-10-226-34-17 varnishd[20204]: Child cleanup complete Mar 2 14:01:21 ip-10-226-34-17 varnishd[20204]: child (13224) Started Mar 2 14:01:21 ip-10-226-34-17 varnishd[20204]: Child (13224) said Closed fds: 4 5 6 10 11 13 14 Mar 2 14:01:21 ip-10-226-34-17 varnishd[20204]: Child (13224) said Child starts Mar 2 14:01:21 ip-10-226-34-17 varnishd[20204]: Child (13224) said managed to mmap 536870912 bytes of 536870912 Mar 2 14:01:21 ip-10-226-34-17 varnishd[20204]: Child (13224) said Ready Mar 2 14:01:35 ip-10-226-34-17 varnishd[20204]: Child (13224) not responding to ping, killing it. Mar 2 14:02:10 ip-10-226-34-17 last message repeated 7 times Mar 2 14:03:15 ip-10-226-34-17 last message repeated 13 times Mar 2 14:03:20 ip-10-226-34-17 varnishd[20204]: Child (13224) not responding to ping, killing it. Mar 2 14:05:53 ip-10-226-34-17 varnishd[20204]: Child (13224) not responding to ping, killing it. Mar 2 14:05:53 ip-10-226-34-17 varnishd[20204]: Child (13224) not responding to ping, killing it. Mar 2 14:05:53 ip-10-226-34-17 varnishd[20204]: Child (13224) died signal=3 Mar 2 14:05:53 ip-10-226-34-17 varnishd[20204]: Child cleanup complete Mar 2 14:05:53 ip-10-226-34-17 varnishd[20204]: child (13288) Started I'm not expecting a solution here but any help just to decode what each line is doing would be very instructive. Many thanks!

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• Change DPI setting in Windows 8.1 for the Logon Screen

  - by jmc302005

  How can the DPI setting be changed for the Logon Screen in Windows 8.1? Microsoft has added per-user DPI settings. But this means that there is no adjustable DPI setting for the Lock/Logon screen. You can change the DPI setting to be the same across all displays and this does affect the icons and font on the lock/logon screen. However, it does not affect any app/program that can run on the lock/logon screen. Ex. I use a 44" flat screen TV for my monitor on my desktop. Big enough for me to sit in my recliner and use my computer. I use the on-screen keyboard most of the time. (I don't want to keep a keyboard next to me.) The problem is that with the new DPI setup the on-screen keyboard takes up nearly half the screen, which is too big. I tried looking through the registry to see if I could find a setting for it. In the key HKEY_USERS\.DEFAULT\Control Panel\Desktop there is a string value named LogicalDPIOverride with a value of -1. I have a feeling this is where I can fix the issue. I tried changing the value to 0 and to 1 with no change in the result. Instead I noticed that after logging out and back in the -1 value was back in the registry. How can I change this default DPI? Can I use the LogPixels string that worked for DPI in Windows 7? Here are two Screen shots, one of the Lock Screen and one of the Logon Screen:

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• Problem IIS 7.0 Locking files durring upload

  - by viscious

  I am running a server 2008 with iis7 and the ftp addon on to iis 7.0 I have the ftp site configured and mostly working Except that about 70% of the time when transferring a file the upload will hang forever. If I disconnect the ftp client and reconnect and try to upload the same file I will get an error on the client saying the file is locked. I have to restart the ftp service to clear the lock. I fired up process explorer and did a search on the file in question and sure enough the ftp service has a lock on the file and it takes around 20 minutes to release the lock on its own (and sometimes longer). This lock stays around even after I disconnect the client. Like I said this only happens about 70% of the time, the other 30% of the time it goes through just fine. Things i have verified. -Not a firewall issue. Server is using passive port range 8000-9000 which is allowed on the firewall. -Not a nat issue, server has a globally rout-able ip address -all recommended/required updates installed I have 5 other servers in a very similar configuration and this is the only one i have problems with.

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• Error when starting qpidd as a service

  - by Sparks

  I have recently swapped from CENTOS 5 to FEDORA 17. Previously I have created my own init.d scripts successfully (albeit not for qpidd) however, in FEDORA I cannot get it to work. I have created the following script (called qpidd) in the init.d directory: #!/bin/bash # # /etc/rc.d/init.d/qpidd # # QPID/AMQP Broker scripts # # # chkconfig: 2345 20 80 # description: QPID/AMQP Broker service # processname: qpidd # pidfile: /var/lock/subsys/qpidd # Source function library. . /etc/init.d/functions SERVICENAME=qpidd start() { echo -n "Starting $SERVICENAME: " daemon qpidd -d & retval=$? touch /var/lock/subsys/$SERVICENAME return $retval } stop() { echo -n "Shutting down $SERVICENAME: " qpidd -q & retval=$? rm -f /var/lock/subsys/$SERVICENAME return $retval } case "$1" in start) start ;; stop) stop ;; status) status qpidd ;; restart) stop start ;; condrestart) [ -f /var/lock/subsys/<service> ] && restart || : ;; *) echo "Usage: $SERVICENAME {start|stop|status|restart" exit 1 ;; esac exit $? After this, I ran chkconfig --add qpidd, however, now when I run sudo service qpidd start I get the following message: Starting qpidd (via systemctl): Job failed. See system journal and 'systemctl status' for details. If I then run systemctl status qpidd I get the following message: Failed to issue method call: Unit name qpidd is not valid. I am now lost, I have search the web and Stack Overflow but cannot find anybody with similar problem, any help or direction to a website that can help would be much appreciated Sparks :)

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• Implications of disabling the AMD Phenom's TLB patch?

  - by DMA57361

  I'm currently running a AMD Phenom X4 9600 processor (yeah, it's aging a bit, but other recent problems mean it's not getting upgraded in the immediate future), which happens to be one of the chips that suffer from the TLB errata. I recall that the first time I played with disabling the TLB patch (probably over a year ago, while playing a game that had a severe performance problem such that it was almost unplayable unless the patch was disabled) I had at least one BSOD, but I can't remeber them being particularly frequent. However, because it decreased instability, I stopped disabling the patch once I was done with the game. Now, after some recent hardware changes I was experiancing much worse performance than expected from the new hardware under some circumstances, and the TLB jumped to mind - after testing I found that disabling the patch would improve the performance to expected levels. I'm now wondering if it's worthwhile always having the patch disabled to avoid any potential slowdowns cropping up in the future, or if it is too dangerous. Everything I read states that the bug, when not patched, can causes a system lock-up in "rare circumstances". So, with the TLB patch disabled: How frequently should system lock-ups be expected? Do we know what the circumstances that trigger the lock-ups are? (Don't worry too much about being highly technical, but essentially I wonder if the chip more vunerable under heavy load, or heavy memory usage, etc?) Are there any secondary problems I should be aware of? (Don't include things that are charateristic to all lock-ups, please)

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• Why is XSP/mono giving me file/write errors with lucence?

  - by acidzombie24

  I am using mono 2.6.7, xsp 2.8.? and i am not sure what else. I'll try downgrading xsp and whatever else. Today i notice my server randomly gets Http Error 500, internal server error. I looked in my log files http://www.pastie.org/1426236 and it appears that the problem is locking lucence which it does by creating a file called write.lock. This use to work with no problem but now it gives me pain. It will fix itself if i refresh the page several times but it will break just as easily. My other site will not work everytime i restart apache and i need to by hand delete the file (at least it doesnt get random 500 errors). However now it just says Lock obtain timed out: NativeFSLock@/var/www/SITE_2/App_Data/LuceneIndex_a/write.lock no matter what. I even chmod -R 777 the directory and still no luck. write.lock doesnt even exist. I have no clue whats going on. Any ideas?

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• XNA Xbox 360 Content Manager Thread freezing Draw Thread

  - by Alikar

  I currently have a game that takes in large images, easily bigger than 1MB, to serve as backgrounds. I know exactly when this transition is supposed to take place, so I made a loader class to handle loading these large images in the background, but when I load the images it still freezes the main thread where the drawing takes place. Since this code runs on the 360 I move the thread to the 4th hardware thread, but that doesn't seem to help. Below is the class I am using. Any thoughts as to why my new content manager which should be in its own thread is interrupting the draw in my main thread would be appreciated. namespace FileSystem { /// <summary> /// This is used to reference how many objects reference this texture. /// Everytime someone references a texture we increase the iNumberOfReferences. /// When a class calls remove on a specific texture we check to see if anything /// else is referencing the class, if it is we don't remove it. If there isn't /// anything referencing the texture its safe to dispose of. /// </summary> class TextureContainer { public uint uiNumberOfReferences = 0; public Texture2D texture; } /// <summary> /// This class loads all the files from the Content. /// </summary> static class FileManager { static Microsoft.Xna.Framework.Content.ContentManager Content; static EventWaitHandle wh = new AutoResetEvent(false); static Dictionary<string, TextureContainer> Texture2DResourceDictionary; static List<Texture2D> TexturesToDispose; static List<String> TexturesToLoad; static int iProcessor = 4; private static object threadMutex = new object(); private static object Texture2DMutex = new object(); private static object loadingMutex = new object(); private static bool bLoadingTextures = false; /// <summary> /// Returns if we are loading textures or not. /// </summary> public static bool LoadingTexture { get { lock (loadingMutex) { return bLoadingTextures; } } } /// <summary> /// Since this is an static class. This is the constructor for the file loadeder. This is the version /// for the Xbox 360. /// </summary> /// <param name="_Content"></param> public static void Initalize(IServiceProvider serviceProvider, string rootDirectory, int _iProcessor ) { Content = new Microsoft.Xna.Framework.Content.ContentManager(serviceProvider, rootDirectory); Texture2DResourceDictionary = new Dictionary<string, TextureContainer>(); TexturesToDispose = new List<Texture2D>(); iProcessor = _iProcessor; CreateThread(); } /// <summary> /// Since this is an static class. This is the constructor for the file loadeder. /// </summary> /// <param name="_Content"></param> public static void Initalize(IServiceProvider serviceProvider, string rootDirectory) { Content = new Microsoft.Xna.Framework.Content.ContentManager(serviceProvider, rootDirectory); Texture2DResourceDictionary = new Dictionary<string, TextureContainer>(); TexturesToDispose = new List<Texture2D>(); CreateThread(); } /// <summary> /// Creates the thread incase we wanted to set up some parameters /// Outside of the constructor. /// </summary> static public void CreateThread() { Thread t = new Thread(new ThreadStart(StartThread)); t.Start(); } // This is the function that we thread. static public void StartThread() { //BBSThreadClass BBSTC = (BBSThreadClass)_oData; FileManager.Execute(); } /// <summary> /// This thread shouldn't be called by the outside world. /// It allows the File Manager to loop. /// </summary> static private void Execute() { // Make sure our thread is on the correct processor on the XBox 360. #if WINDOWS #else Thread.CurrentThread.SetProcessorAffinity(new int[] { iProcessor }); Thread.CurrentThread.IsBackground = true; #endif // This loop will load textures into ram for us away from the main thread. while (true) { wh.WaitOne(); // Locking down our data while we process it. lock (threadMutex) { lock (loadingMutex) { bLoadingTextures = true; } bool bContainsKey = false; for (int con = 0; con < TexturesToLoad.Count; con++) { // If we have already loaded the texture into memory reference // the one in the dictionary. lock (Texture2DMutex) { bContainsKey = Texture2DResourceDictionary.ContainsKey(TexturesToLoad[con]); } if (bContainsKey) { // Do nothing } // Otherwise load it into the dictionary and then reference the // copy in the dictionary else { TextureContainer TC = new TextureContainer(); TC.uiNumberOfReferences = 1; // We start out with 1 referece. // Loading the texture into memory. try { TC.texture = Content.Load<Texture2D>(TexturesToLoad[con]); // This is passed into the dictionary, thus there is only one copy of // the texture in memory. // There is an issue with Sprite Batch and disposing textures. // This will have to wait until its figured out. lock (Texture2DMutex) { bContainsKey = Texture2DResourceDictionary.ContainsKey(TexturesToLoad[con]); Texture2DResourceDictionary.Add(TexturesToLoad[con], TC); } // We don't have the find the reference to the container since we // already have it. } // Occasionally our texture will already by loaded by another thread while // this thread is operating. This mainly happens on the first level. catch (Exception e) { // If this happens we don't worry about it since this thread only loads // texture data and if its already there we don't need to load it. } } Thread.Sleep(100); } } lock (loadingMutex) { bLoadingTextures = false; } } } static public void LoadTextureList(List<string> _textureList) { // Ensuring that we can't creating threading problems. lock (threadMutex) { TexturesToLoad = _textureList; } wh.Set(); } /// <summary> /// This loads a 2D texture which represents a 2D grid of Texels. /// </summary> /// <param name="_textureName">The name of the picture you wish to load.</param> /// <returns>Holds the image data.</returns> public static Texture2D LoadTexture2D( string _textureName ) { TextureContainer temp; lock (Texture2DMutex) { bool bContainsKey = false; // If we have already loaded the texture into memory reference // the one in the dictionary. lock (Texture2DMutex) { bContainsKey = Texture2DResourceDictionary.ContainsKey(_textureName); if (bContainsKey) { temp = Texture2DResourceDictionary[_textureName]; temp.uiNumberOfReferences++; // Incrementing the number of references } // Otherwise load it into the dictionary and then reference the // copy in the dictionary else { TextureContainer TC = new TextureContainer(); TC.uiNumberOfReferences = 1; // We start out with 1 referece. // Loading the texture into memory. try { TC.texture = Content.Load<Texture2D>(_textureName); // This is passed into the dictionary, thus there is only one copy of // the texture in memory. } // Occasionally our texture will already by loaded by another thread while // this thread is operating. This mainly happens on the first level. catch(Exception e) { temp = Texture2DResourceDictionary[_textureName]; temp.uiNumberOfReferences++; // Incrementing the number of references } // There is an issue with Sprite Batch and disposing textures. // This will have to wait until its figured out. Texture2DResourceDictionary.Add(_textureName, TC); // We don't have the find the reference to the container since we // already have it. temp = TC; } } } // Return a reference to the texture return temp.texture; } /// <summary> /// Go through our dictionary and remove any references to the /// texture passed in. /// </summary> /// <param name="texture">Texture to remove from texture dictionary.</param> public static void RemoveTexture2D(Texture2D texture) { foreach (KeyValuePair<string, TextureContainer> pair in Texture2DResourceDictionary) { // Do our references match? if (pair.Value.texture == texture) { // Only one object or less holds a reference to the // texture. Logically it should be safe to remove. if (pair.Value.uiNumberOfReferences <= 1) { // Grabing referenc to texture TexturesToDispose.Add(pair.Value.texture); // We are about to release the memory of the texture, // thus we make sure no one else can call this member // in the dictionary. Texture2DResourceDictionary.Remove(pair.Key); // Once we have removed the texture we don't want to create an exception. // So we will stop looking in the list since it has changed. break; } // More than one Object has a reference to this texture. // So we will not be removing it from memory and instead // simply marking down the number of references by 1. else { pair.Value.uiNumberOfReferences--; } } } } /*public static void DisposeTextures() { int Count = TexturesToDispose.Count; // If there are any textures to dispose of. if (Count > 0) { for (int con = 0; con < TexturesToDispose.Count; con++) { // =!THIS REMOVES THE TEXTURE FROM MEMORY!= // This is not like a normal dispose. This will actually // remove the object from memory. Texture2D is inherited // from GraphicsResource which removes it self from // memory on dispose. Very nice for game efficency, // but "dangerous" in managed land. Texture2D Temp = TexturesToDispose[con]; Temp.Dispose(); } // Remove textures we've already disposed of. TexturesToDispose.Clear(); } }*/ /// <summary> /// This loads a 2D texture which represnets a font. /// </summary> /// <param name="_textureName">The name of the font you wish to load.</param> /// <returns>Holds the font data.</returns> public static SpriteFont LoadFont( string _fontName ) { SpriteFont temp = Content.Load<SpriteFont>( _fontName ); return temp; } /// <summary> /// This loads an XML document. /// </summary> /// <param name="_textureName">The name of the XML document you wish to load.</param> /// <returns>Holds the XML data.</returns> public static XmlDocument LoadXML( string _fileName ) { XmlDocument temp = Content.Load<XmlDocument>( _fileName ); return temp; } /// <summary> /// This loads a sound file. /// </summary> /// <param name="_fileName"></param> /// <returns></returns> public static SoundEffect LoadSound( string _fileName ) { SoundEffect temp = Content.Load<SoundEffect>(_fileName); return temp; } } }

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• C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

  - by James Michael Hare

  So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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• Plagued by multithreaded bugs

  - by koncurrency

  On my new team that I manage, the majority of our code is platform, TCP socket, and http networking code. All C++. Most of it originated from other developers that have left the team. The current developers on the team are very smart, but mostly junior in terms of experience. Our biggest problem: multi-threaded concurrency bugs. Most of our class libraries are written to be asynchronous by use of some thread pool classes. Methods on the class libraries often enqueue long running taks onto the thread pool from one thread and then the callback methods of that class get invoked on a different thread. As a result, we have a lot of edge case bugs involving incorrect threading assumptions. This results in subtle bugs that go beyond just having critical sections and locks to guard against concurrency issues. What makes these problems even harder is that the attempts to fix are often incorrect. Some mistakes I've observed the team attempting (or within the legacy code itself) includes something like the following: Common mistake #1 - Fixing concurrency issue by just put a lock around the shared data, but forgetting about what happens when methods don't get called in an expected order. Here's a very simple example: void Foo::OnHttpRequestComplete(statuscode status) { m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } So now we have a bug in which Shutdown could get called while OnHttpNetworkRequestComplete is occuring on. A tester finds the bug, captures the crash dump, and assigns the bug to a developer. He in turn fixes the bug like this. void Foo::OnHttpRequestComplete(statuscode status) { AutoLock lock(m_cs); m_pBar->DoSomethingImportant(status); } void Foo::Shutdown() { AutoLock lock(m_cs); m_pBar->Cleanup(); delete m_pBar; m_pBar=nullptr; } The above fix looks good until you realize there's an even more subtle edge case. What happens if Shutdown gets called before OnHttpRequestComplete gets called back? The real world examples my team has are even more complex, and the edge cases are even harder to spot during the code review process. Common Mistake #2 - fixing deadlock issues by blindly exiting the lock, wait for the other thread to finish, then re-enter the lock - but without handling the case that the object just got updated by the other thread! Common Mistake #3 - Even though the objects are reference counted, the shutdown sequence "releases" it's pointer. But forgets to wait for the thread that is still running to release it's instance. As such, components are shutdown cleanly, then spurious or late callbacks are invoked on an object in an state not expecting any more calls. There are other edge cases, but the bottom line is this: Multithreaded programming is just plain hard, even for smart people. As I catch these mistakes, I spend time discussing the errors with each developer on developing a more appropriate fix. But I suspect they are often confused on how to solve each issue because of the enormous amount of legacy code that the "right" fix will involve touching. We're going to be shipping soon, and I'm sure the patches we're applying will hold for the upcoming release. Afterwards, we're going to have some time to improve the code base and refactor where needed. We won't have time to just re-write everything. And the majority of the code isn't all that bad. But I'm looking to refactor code such that threading issues can be avoided altogether. One approach I am considering is this. For each significant platform feature, have a dedicated single thread where all events and network callbacks get marshalled onto. Similar to COM apartment threading in Windows with use of a message loop. Long blocking operations could still get dispatched to a work pool thread, but the completion callback is invoked on on the component's thread. Components could possibly even share the same thread. Then all the class libraries running inside the thread can be written under the assumption of a single threaded world. Before I go down that path, I am also very interested if there are other standard techniques or design patterns for dealing with multithreaded issues. And I have to emphasize - something beyond a book that describes the basics of mutexes and semaphores. What do you think? I am also interested in any other approaches to take towards a refactoring process. Including any of the following: Literature or papers on design patterns around threads. Something beyond an introduction to mutexes and semaphores. We don't need massive parallelism either, just ways to design an object model so as to handle asynchronous events from other threads correctly. Ways to diagram the threading of various components, so that it will be easy to study and evolve solutions for. (That is, a UML equivalent for discussing threads across objects and classes) Educating your development team on the issues with multithreaded code. What would you do?

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• deadlocks in the innodb status

  - by shantanuo

  Mysql sever has suddenly become very slow. There are no queries in the slow query log but the innodb status shows something like the following. Does it mean that it is due to innodb deadlock? if Yes, what is the way out? *************************** 1. row *************************** Status: ===================================== 100315 12:55:29 INNODB MONITOR OUTPUT ===================================== Per second averages calculated from the last 5 seconds ---------- SEMAPHORES ---------- OS WAIT ARRAY INFO: reservation count 187532, signal count 188120 Mutex spin waits 0, rounds 61908654, OS waits 33052 RW-shared spins 89241, OS waits 41948; RW-excl spins 5857, OS waits 1557 ------------------------ LATEST DETECTED DEADLOCK ------------------------ 100315 12:43:02 *** (1) TRANSACTION: TRANSACTION 0 56996536, ACTIVE 0 sec, process no 5000, OS thread id 3031395216 starting index read mysql tables in use 1, locked 1 LOCK WAIT 6 lock struct(s), heap size 1024, undo log entries 6 MySQL thread id 994, query id 7699751 localhost application Searching rows for update UPDATE QUERY *** (1) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 0 page no 4073 n bits 296 index `PRIMARY` of table `dbII/tbl_ticket_block_master` trx id 0 56996536 lock_mode X locks r ec but not gap waiting Record lock, heap no 141 PHYSICAL RECORD: n_fields 23; compact format; info bits 0 0: len 7; hex 33353837393936; asc 3587996;; 1: len 4; hex 800001f4; asc ;; 2: len 1; hex 47; asc G;; 3: len 2; hex 6f6b; asc ok;; 4: le n 6; hex 0000035957fe; asc YW ;; 5: len 7; hex 000000401737c0; asc @ 7 ;; 6: SQL NULL; 7: SQL NULL; 8: SQL NULL; 9: len 3; hex 8fb46e; asc n;; 10: SQL NULL; 11: len 1; hex 30; asc 0;; 12: len 0; hex ; asc ;; 13: SQL NULL; 14: len 1; hex 33; asc 3;; 15: len 4; hex 4b9ceebe ; asc K ;; 16: len 1; hex 30; asc 0;; 17: len 4; hex 80006ae8; asc j ;; 18: len 0; hex ; asc ;; 19: len 0; hex ; asc ;; 20: len 0; hex ; asc ;; 21: len 0; hex ; asc ;; 22: len 0; hex ; asc ;; *** (2) TRANSACTION: TRANSACTION 0 56996527, ACTIVE 0 sec, process no 5000, OS thread id 2961476496 fetching rows, thread declared inside InnoDB 237 mysql tables in use 3, locked 3 121 lock struct(s), heap size 11584, undo log entries 16 MySQL thread id 995, query id 7699729 localhost application Searching rows for update UPDATE QUERY *** (2) HOLDS THE LOCK(S): RECORD LOCKS space id 0 page no 4073 n bits 296 index `PRIMARY` of table `DBII/tbl_ticket_block_master` trx id 0 56996527 lock_mode X Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0 0: len 8; hex 73757072656d756d; asc supremum;; Record lock, heap no 2 PHYSICAL RECORD: n_fields 23; compact format; info bits 0 0: len 7; hex 33353837343631; asc 3587461;; 1: len 4; hex 800001f4; asc ;; 2: len 1; hex 47; asc G;; 3: len 6; hex 497373756564; asc Is sued;; 4: len 6; hex 000003425295; asc BR ;; 5: len 7; hex 8000000464012c; asc d ,;; 6: SQL NULL; 7: len 4; hex 80000058; asc X;; 8: len 1; hex 43; asc C;; 9: len 3; hex 8fb465; asc e;; 10: len 3; hex 8fb46d; asc m;; 11: len 1; hex 30; asc 0;; 12: len 0; hex ; asc ; ; 13: SQL NULL; 14: len 1; hex 33; asc 3;; 15: len 4; hex 4b9b33a2; asc K 3 ;; 16: len 3; hex 756d67; asc umg;; 17: len 4; hex 80006744; asc gD;; 18: len 0; hex ; asc ;; 19: len 0; hex ; asc ;; 20: len 0; hex ; asc ;; 21: len 0; hex ; asc ;; 22: len 0; hex ; asc ;;

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